There are many dye
and print works in which large quantities of these extracts are used
without being subjected to trustworthy tests. Moreover, much of the
testing is done by fallacious methods and often by biased hands. So
fallacious, indeed, are some of these tests, that grossly adulterated
extracts are often declared superior to the purer ones, the cause of
this being the application of an insufficient proportion of mordant in
the dyeing or printing trials, and the consequent waste of the excess
of coloring matter in the case of the purer preparation.
Professional analytical chemists have hitherto given but little
attention to these preparations, and the employment of experienced
chemists in works is as yet far from general. The testing of dyewood
extracts in such a manner as to throw full light on their purity, the
quality of raw material from which they are prepared, their exact
commercial value their suitability for special purposes, and the
proportion and nature of any adulterants they may contain, is of
course a difficult and tedious task, and must be left to the expert
who is in possession of authentic specimens prepared by himself of all
the different extracts made from every variety and quality of raw
materials, and who combines a thorough knowledge of experimental
dyeing and printing with a large experience in the chemical
investigation of these preparations.
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